Method of separation and liquefaction of gases



Dec. 4-, 1928.

1,694,308 w. s. BOWEN METHOD OF SEPARATION AND LIQUEFACTION OF GASES Filed Jan. 11., 1,927

Patented Dec. 4, 1928.

UNITED STATES.

WILLIAM SPENCER BOWEN, F WESTFIELD, NEW JERSEY.

METHOD OF S EPARATION AND LIQUEFACTION OF GASES.

Application filed January 11, 1927. Serial No. 160,446.

- gases from said mixture is accomplished by liqnefying.

The. principal object of the invention is to bring successive portions of a progressively flowing column of the gas mixture into heat I interchanging relationship, under such conditions of high pressure as may be naturally encountered, and at such temperature of the one portion as will liquefy one of the gaseous constituents of the mixture at that pressure, provision being made for a pressure drop between the successive portions of mixture, to atmospheric or any other convenient pressure, whereby the critical temperature is lowered proportionately to the pressure drop, the conditions of liquefaction being thus continued down into the realms of low pressure so that a continuous supply of liquefied gas is produced and maintained available for use at low pressure.

Other objects of the invention will appear as a description of the following illustrative, and largely diagrammatic, embodiment of apparatus proceeds, by which the method which constitutes one phase of invention may be practiced.

In the drawings the sole figure represents a side elevation, partly in section, of apparatus illustrating my invention, in which the numeral 1 represents a conduit, the end 2 of which is assumed to be in communication with a mixture of, gases under high pressure. In the present instance the invention is assumed to be practiced in the segregation of methane from natural gas, and the end 2 of the conduit 1 may be connected directly to a high pressure gas well, or to a compressor in case the natural pressure is not high enough to accomplish the purpose of the invention. The conduit 1 passes successively through the serially connected countercurrent interchangers 3, 4, 5 and 6, of which there may be any number, between which interchangers traps 7, 8, 9 and 10 are connected to the conduit, the purpose of said traps being to collect any vapors of the gaseous mixture which may have become condensed through the cooling action of the interchangers. It is quite important that the gaseous mixture be thus dried before the final liquefaction of the methane to prevent the deposit of frost on the interior surface of the conduits especially in that region in which the temperature approaches the critical temperature of the methane.

The conduit 1 is preferably formed with a vertical limb 11 which passes through a vertical interchanger 12. The limb 11 communicates with the chamber of the interchan'ger 12 by means of orifices 13, and the upper part of the interchanger 12 is in communication by means of the pipe 14 with the series of interchangers 6,5, 4 and 3. The process of the invention may be fully carried out by the apparatus which has now been described, but the drawing illustrates a branch conduit 15 communicating with the vertical limb 11 of the conduit 1, said branch conduit being connected to a second conduit corresponding to the conduit 2 which is associated with a second set of interchangers and traps for alternative use when the first described conduit and series of interchangers and traps are cut off for purpose of repair or for any other reason. Valves 16 and 17 are shown for putting either the conduit 1 or branch conduit 15 into operative communication with the conduit 11.

In the operation of my invention, gas under high pressure passes through the conduit 1 in the direction of the arrow, the moisture of any gaseous constituents which are liquefiable at relatively high temperatures being condensed and retained by the series of'traps 7 to 10. The gaseous mixture then proceeds into the limb 1.1 of the conduit 1, the unliquefied or cooled gases expanding from high pressure to atmospheric or some other lower convenient pressure through the orifices 13, into the interchanger 12.

Now since the gaseous mixture in the vertical limb 11. is under high pressure and is conveniently subjected to countercurrent cooling of regenerative type, the temperature of the gas to be separated from the mixture will ultimately fall to arpoint at which lique-' faction will take place within the limb 11.

Also as this cold gas, vapor, vapor-liquid mixture and any liquid condensate thereof, expands through the orifices13 into the interchanger 12, vapor and liquid at atmospheric pressure will result. The temperature of the vapor-liquid mixture in the interohanger 12 will'be that of the boiling point of the liquid at atmospheric pressure. Now this temperature is very much lower than cided interchange of heat between the conduit 11 and inter-changer 12, which will cause liquefaction of the gas or vapor in the conduit 11, and boiling of the liquid of said vapor in the interchanger 12. Since the latent heat of condensation of the vapor in conduit 11 due to its high pressure is less than the latent heat of vaporization of the liquid in the interchanger 12, the latter liquid will tend to accumulate in quantity so that it can be drawnofl' at a fixed rate through the valve 18 and at a point above theorifices 13, which are thus submerged in the liquefied gas. Also, as the quantity of said liquid increases it will rise in the interchanger 12 to some point determined by the combined effect ofthe rate of ebullition in the interchanger 12,- and the rate at which liquid is drawn off through the valve 18. The result is that the liquid formed in the conduit 11 under high pressure, at a high point in said conduit, at, say, 19, will be at a higher temperature than the liquid in said conduit at a point adjacent the orifices 13.

Come uently, the liquid in the conduit 11,

upon owing through. the orifices 13 will not even partially vaporlze when-theapparatus has been in operation for some time,

but will continue as a liquid in the inter-.

changer 12.

While attention has been directed chiefly to that gas of the mixture which it is intended to segregate by liquefaction, it is to be understood that those constituents of the gaseous mixture which are unliquefiable at the low temperature attained by the interchanger 12, will pass upwardly along with the vapor of ebullition of the liquid in said interehanger, the cold gases and vapor flowing to the series of interchangers 6 to 3 inclusive by way of the pipe 14:, in a countercurrent direction.

Although I have in the present description defined my invention in terms of a very elemental and diagrammatic layout of apparatus, it is to be understood thatthe broad principle of the invention (which concerns itself with the liquefaction of a gas, normally met with at relatively high pressure, by the regenerative maintenance of the critical tem perature of said gas throughout a pressure drop," whereby said gas is segregated from a. gaseous mixture of which it may be a component, and made available for use at low pressure) may find practical embodiment in many forms of apparatus which may be devised from time to time as knowledge of the uses of the invention increases.

Having described my invention what I claim as new and desire'to secure by Letters Patent, is

The method of segregating a gas from a mixture of gases, which consists in passing a column of gaseous mixture at high pressure through a restricted opening, from one cham ber to another, thereby reducing it to low pressure and to a temperature below the critical temperature of one of said gases at said low pressure, regeneratively cooling the advance portion of said column by gas liquefied at said lower than critical temperature, and the rearward portion of said column, by the ebullition temperature of said gas collecting the liquefied gas, and maintaining the restricted opening submerged in the liquefied gas.

In testimony whereof I have hereunto set my hand.

WILLIAM SPENCER BOlVEN. 

